Bring back convert nerf to fix overweighted taiko difficulty

[smoogipoo]

See discussion leading on from: https://discord.com/channels/188630481301012481/542532479626772500/1300899520023892030

In particular, scores like https://osu.ppy.sh/scores/3769125529 are worth 1400pp and are now the PP record.

This reverts the convert-related diffcalc change in #20558 .

[smoogipoo]

!diffcalc
RULESET=taiko

[github-actions]

Target: #30456
Spreadsheet: https://docs.google.com/spreadsheets/d/1BRQARTALvsg33esPb7EfjaAQrmjVOm5BzZtkrTyu_0g/edit

[Lawtrohux]

#30460 aims to specifically target the issue that's giving pp record (high bpm single-coloured streams) in a way that doesn't affect all converts, however with converts consistently becoming an issue due them breaking all the concepts behind difficulty calculation, this may be necessary.

I also think the discussion of converts giving pp values needs to be raised too, I've been seeing/receiving a lot of community discontent in regards to converts at this point in time. I remain neutral.